Giải thích các bước giải:
Ta có :
$A=\dfrac{1}{5}+(\dfrac{1}{14}+\dfrac{1}{28}+\dfrac{1}{44})+(\dfrac{1}{61}+\dfrac{1}{85}+\dfrac{1}{97})$
$\to A<\dfrac{1}{5}+(\dfrac{1}{12}+\dfrac{1}{12}+\dfrac{1}{12})+(\dfrac{1}{60}+\dfrac{1}{60}+\dfrac{1}{60})$
$\to A<\dfrac{1}{5}+\dfrac{3}{12}+\dfrac{3}{60}=\dfrac{1}{2}$